PAA Content Research Articles

Negative impact of poly(acrylic acid) on proton conductivity of electrospun catalyst layers

The electrospun catalyst layers (E-spun CLs) have attracted great attention recently owing to their decent performance and durability compared to conventional coated CL fabricated by scrape coating. However, proton transport in E-spun CLs is poorly understood, hindering further performance improvements. We unravel herein that the high molecular weight (MW) polymer used to form nanofibers, usually Poly(acrylic acid) (PAA), is a key factor affecting the proton conductivity. Nuclear magnetic resonance (NMR) unravels strong interaction between the ionomer and PAA. The proton conductivity of ionomer membranes with varying PAA content under different ionomer volume fractions and relative humidity (RH) was quantitatively assessed using the four-probe electrochemical impedance spectroscopy (EIS). E-spun CL exhibited lower proton conductivity than coated CL or pseudo catalyst layer (PCL) at the same ionomer volume fraction due to the detrimental effects of PAA. The proton transport tortuosity of E-spun CL increased with RH, likely attributed to the significant swelling ratio of PAA. The proton transport tortuosity of E-spun CL displayed less sensitivity to the ionomer volume fraction, which can be attributed to the homogeneous distribution of the ionomer within the nanofibers. Our work implies that the key to enhancing proton conductivity of E-spun CLs is to remove PAA completely, or to replace PAA with alternatives that would not impair proton transport.

Porous polymer cement composites for quasi-solid graphene supercapacitors

We reported a strong and cheap polymer modified Portland cement (PC) composites with interconnected pores as solid electrolyte for graphene supercapacitors. The porous polymer cement composites solved the low ionic conductivity question of construction materials. Herein, the effects of PAA molecular weight, PAA content and curing age on electrical energy storage and mechanical property were investigated in detail. The PAA (Mw = 5000)/PC-5 % sample delivers the best multifunctionality. Moreover, the as-assembled solid supercapacitor exhibits an optimum energy density of 15.93 mW h cm−2, as well as a considerable compressive strength of 16.2 MPa at 28 days. In addition, introducing PAA can result in high porosity which is conductive to ion migration. The symmetric electrode is directly loaded with GO on Ni foam by electrophoretic, followed by high temperature thermal reduction. The integrated solid supercapacitors are effective, holistic and effortless to operate at room temperature, and they exert a crucial role in energy storage field of inorganic building materials application.

Dramatically enhancing mechanical properties of hydrogels by drying reactive polymers at elevated temperatures to introduce strong physical and chemical crosslinks

Mechanically strong and tough hydrogels have a wide range of practical applications, and many preparation methods have been developed in recent two decades. However, facile and convenient methods for preparing hydrogels with excellent mechanical properties are still lacking. In this work, we report a strategy for preparing hydrogels with very high mechanical strengths by utilizing the strong physical and chemical crosslinks formed by drying reactive polymers at elevated temperatures. The obtained polyvinyl alcohol-polyacrylic acid (PVA-PAA) hydrogels show very high tensile strengths and elastic moduli up to 28.9 MPa and 26.6 MPa, which are several tens and hundreds of times those of PVA-PAA hydrogels prepared with freezing-thawing method, respectively. And the mechanical properties of the hydrogels can be adjusted by controlling drying temperature and PAA content. The crosslinking nature of the hydrogels are studied and proved with swelling and rheology measurements as well as structural characterizations. The drying at elevated temperatures enables the occurrence of esterification reaction and promotes the crystallization of PVA chains and the formation of stronger hydrogen bonds between PVA and PAA chains. This work provides a simple and facile method to prepare high-strength hydrogels for wide potential applications.

A Study on the Dual Thermo- and pH-Responsive Behaviors of Well-Defined Star-like Block Copolymers Synthesize by Combining of RAFT Polymerization and Thiol-Ene Click Reaction.

A series of stimuli-responsive star-like block copolymers are synthesized via the combination of reversible addition, fragmentation chain transfer (RAFT) polymerization, and photo-initiated thiol-ene (PITE) click reaction. The controllable block ratio and block sequence, narrow distribution of molecular weight, and customized arm numbers of the star-shaped copolymers reveal the feasibility and benefits of combination of RAFT polymerization and PITE click reaction for synthesis of well-defined star-like (co)polymers. A clear insight into the relationship among the arm number, block sequence, and block ratio of the star-like block copolymers and their stimuli-responsive aggregation behavior was achieved via dynamic light scattering and UV-vis spectroscopy study. Notably, the star-like poly(acrylic acid)-b-poly(2-(dimethylamino) ethyl methacrylate) (star-PAA-b-PDMAEMA) shows higher lower critical solution temperature (LCST) compared to star-PDMAEMA-b-PAA with the same arm number and block ratio due to the inner charged PAA segments at pH > IEP. In addition, for star-like PAA-b-PDMAEMA, higher PAA content enhances the hydrophilicity of the polymer in basic solution and leads to the LCST increase, except for star-PAA1-b-PDMAEMA4 at pH = 9.0 (IEP). For star-PDMAEMA-b-PAA, the PAA content shows minimal effect on their LCSTs, except for the polymer in solution with pH = 9.5, which is far from their IEP. The star-like block copolymers with well-defined structure and tunable composition, especially the facile-controlled block sequence, bring us a challenging opportunity to control the stimuli-responsive properties of star-like block copolymers.

Effects of high polyamic acid content and curing process on properties of epoxy resins

Abstract Epoxy/polyamic acid (EP/PAA) adhesives with high polyimide precursor-PAA content have been synthesized and then cured. The structure, thermal, and adhesive properties were investigated by Fourier transform infrared spectroscopy, thermogravimetric analysis, and tensile shear test. The effects of PAA content and curing process on the tensile shear strength were also studied. The results showed that the addition of PAA improved the heat resistance and reduced the water absorption. EP/PAA adhesive kept good adhesion. A kind of EP/PAA composite adhesive with excellent comprehensive properties was prepared in this study.

Electrospinning Ethanol–Water Solutions of Poly(Acrylic Acid): Nonlinear Viscosity Variations and Dynamic Taylor Cone Behavior

AbstractElectrospinning of polymer solutions is a multifaceted process that depends on the careful balancing of many parameters to achieve a desired outcome, in many cases including mixtures of multiple solvents. A systematic study of how the solution viscosity —a good probe of solvent–polymer interactions—and the electrospinnability change when poly(acrylic acid) (PAA) is dissolved in ethanol–water mixtures at varying mixing ratio is carried out. A pronounced maximum is found in at a water‐to‐ethanol molar ratio of about 2:1, where the solvent mixture deviates maximally from ideal mixing behavior and partial deprotonation of carboxyl groups by water coincides synergistically with dissolution of the uncharged protonated PAA fraction by ethanol. The PAA concentration is tuned as a function of water–ethanol ratio to obtain a common value of for all solvent mixtures that is suitable for electrospinning. For high PAA content, the Taylor cone grows in volume over time despite minimum solution flow rate, even experiencing surface gelation for ethanol‐rich solutions. This is attributed to the hygroscopic nature of PAA, drawing excess water into the Taylor cone from the air during spinning.

Injectable Enzymatically Hardened Calcium Phosphate Biocement.

(1) Background: The preparation and characterization of novel fully injectable enzymatically hardened tetracalcium phosphate/monetite cements (CXI cements) using phytic acid/phytase (PHYT/F3P) hardening liquid with a small addition of polyacrylic acid/carboxymethyl cellulose anionic polyelectrolyte (PAA/CMC) and enhanced bioactivity. (2) Methods: Composite cements were prepared by mixing of calcium phosphate powder mixture with hardening liquid containing anionic polyelectrolyte. Phase and microstructural analysis, compressive strength, release of ions and in vitro testing were used for the evaluation of cement properties. (3) Results: The simple possibility to control the setting time of self-setting CXI cements was shown (7–28 min) by the change in P/L ratio or PHYT/F3P reaction time. The wet compressive strength of cements (up to 15 MPa) was close to cancellous bone. The increase in PAA content to 1 wt% caused refinement and change in the morphology of hydroxyapatite particles. Cement pastes had a high resistance to wash-out in a short time after cement mixing. The noncytotoxic character of CX cement extracts was verified. Moreover, PHYT supported the formation of Ca deposits, and the additional synergistic effect of PAA and CMC on enhanced ALP activity was found, along with the strong up-regulation of osteogenic gene expressions for osteopontin, osteocalcin and IGF1 growth factor evaluated by the RT-qPCR analysis in osteogenic αMEM 50% CXI extracts. (4) Conclusions: The fully injectable composite calcium phosphate bicements with anionic polyelectrolyte addition showed good mechanical and physico-chemical properties and enhanced osteogenic bioactivity which is a promising assumption for their application in bone defect regeneration.

Synthesis and characterization of biocompatible semi-interpenetrating polymer networks based on polyurethane and cross-linked poly (acrylic acid)

Semi-interpenetrating polymer networks (semi-IPNs) of polyether-based polyurethane (PU)/cross-linked poly (acrylic acid) (PAA) were synthesized with different PAA content. The PAA was cross-linked by a novel acrylic-urethane diene monomer synthesized by the condensation reaction of hexamethylene diisocyanate (HDI) and acrylic acid (AA). The resulting PU-PAA semi-IPNs were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and tensile measurements. The presence of urethane groups in the cross-linking agent led to better interactions between PAA and PU. Elongation at break of the semi-IPNs increased by increasing the PAA content, while there is a decrease in tensile modulus and strength. PU-PAA-5 had the highest tensile strain, of 1240%. The hydrophobicity of the prepared specimens was investigated by the contact angle drop test and water absorption. The results showed that the hydrophilicity was increased by increasing the PAA content in the semi-IPNs. For PU-PAA-0 to PU-PAA-35, the water contact angle decreased from 82 to 57°. Also confirmed by Methylthiazol tetrazolium (MTT) assay and cell staining, the hydrophilicity directly affected the biocompatibility of the semi-IPNs. These results showed that the PU-PAA semi-IPNs could be a suitable biocompatible material for diverse medical applications.

Role of Phytohormones in Soybean (Glycine max) Seed Development

Phytohormones play a key important role in the sink development of the seed. Endogenous content of IAA, PAA, GA, ABA, and kinetin were estimated in two distinct varieties of soybean (Glycinemax (L.) Merr.) during the entire period of seed development. Antibodies against IAA, PAA, GA, ABA, and kinetin were raised in rabbits. By competitive ELISA, hormones were estimated from the two different varieties: Large seeded variety (L seed) and Small seeded variety (S seed). Growth analysis showed that L seed had more dry weight, the rate of dry matter accumulation and water content than S seed. Plant hormones are signal molecules that regulate many developmental processes, including sink size and dry matter accumulation in viable mature seed. In both the varieties, the free IAA increased gradually with the seed age; value was near to double in L seed. PAA was also observed higher in L seed than S seed during cell elongation period. While GA content was higher in S seed in compare to IAA and PAA. ABA content was observed 2–4 times lower as compared S seed. A significant difference was observed in kinetin levels which showed nearly 1.5 times higher in L seed compared to S seed. GA and ABA levels were more in S seed suggest that GA/ABA ratio and total hormonal balance determine the sink size. The probable role of hormones in seed development is discussed.

Variation in content of tyramine, histamine, 2‐phenylethylamine, tryptamine and their precursor amino acids in a Chardonnay wine by using different commercial active dry yeasts and nitrogen sources

SummaryWine is a fermented beverage that could be affected by high concentrations of biogenic amines, thus altering organoleptic and health properties. In this work, the capacity of different selected yeast strains regarding to affect the content of tyramine, histamine, 2‐phenylethylamine, tryptamine and their precursor amino acids (pAA) during fermentation has been described. Overall, biogenic amines (BAs) and pAA contents appeared significantly related both to the strain and to the nutrient supplementation applied. Among BAs, without and (with) nitrogen source addition, the concentrations covered a range between 0.1 and 9.5 (0.1–10.3) mg L−1 for tyramine; 0.1 and 4.4 (0.1–4.6) mg L−1 for histamine; 0.4 and 1.1 (0.4–1.4) mg L−1 for 2‐phenylethylamine; and 0.02 and 0.14 (0.01–0.12) mg L−1 for tryptamine, respectively. Considering that also wine yeast species are responsible for BAs formation, the evidence from fermentation trials underlined the relevance of a careful choice of ADY strains and nitrogen sources in the management of alcoholic fermentation in wine.

Development of potentially biocompatible hydrogels with cylindrical pores prepared from polyvinyl alcohol and low‐molecular weight polyacrylic acid

In the present work, blend hydrogels from PVA and two different low PAA molecular weights, Mw 1800 g/mol and 5000 g/mol were prepared through the freezing thawing (F‐T) physical crosslinking method. The obtained materials were fully characterized by means of scanning electron microscopy (SEM) in order to analyze their morphology, gel fraction (GF) to determine the crosslinking degree and Fourier transformed infrared spectroscopy (FTIR) to analyze the PVA‐PAA interactions. Thermal characterizations [thermogravimetric analysis (TGA) and dynamic scanning calorimetry (DSC)] were conducted to study the relevant thermal characteristics. Sorption tests at different pH values (4 and 7) obtained from different aqueous systems were also inquired. The effects of PAA contents (between 1 and 5 wt%) and Mw of the used PAA on the hydrogel final properties were analyzed and related to the most probably PVA‐PAA interactions. POLYM. ENG. SCI., 59:1479–1488 2019. © 2019 Society of Plastics Engineers

Stabilization of a novel mixed solution precursor used for preparing YSZ abradable sealing coatings

The mixed solution precursor was prepared by adding the yttria stabilized zirconia (YSZ) nano-particles into the YSZ solution precursor to obtain the ceramic-based abradable sealing nanostructure coatings with the plasma spraying. The stability of the solution precursor must have the fluidity and take precautions to prevent the nano-particles sedimentation too quickly in the tube, resulting in clogging during the spraying process. The measurement of Zeta potential and rheology with varying dispersant were used to research the stabilization and the viscosity of the mixed solution precursor. The microstructure changed, and the phase composition of the mixed solution precursor coatings were evaluated via scanning electronic microscopy (SEM) and X-ray diffractograms (XRD). The result showed that the Zeta potential value and the liquidity of mixed solution precursor improved after using Poly (acrylic acid) (PAA) as a dispersant. The viscosity significant changed as the PAA content, the nano-particles, and the concentration of the precursor solution increased. The suspension plasma spraying (SPS) and solution precursor plasma spraying (SPPS) were combined to obtain a more complex structure in the coating microstructure of the mixed solution precursor with macropores and micropores. This contributed to further improve the structure diversity of coatings. More importantly, the mixed solution precursor coating has the lowest friction coefficient is 0.3 and exhibited the characteristic of excellent tribological performance.

Reversible Protein Adsorption on PMOXA/PAA Based Coatings: Role of PAA

In this study we report design of stimuli-responsive coating based on poly(2-methyl-2-oxazoline-random-glycidyl methacrylate) (PMOXA-r-GMA) comb copolymer and poly(acrylic acid)-block-poly(glycidyl methacrylate) (PAA-b-PGMA) block copolymers and scrutinize its ability to control protein adsorption. Firstly, PMOXA/PAA based coatings were prepared by simply spin coating the mixture of PMOXA-r-GMA and PAA-b-PGMA copolymer solutions onto silicon substrates followed by annealing at 110 °C. Then coatings were rigorously characterized by X-ray photoelectron spectroscopy (XPS), the static water contact angle (WCA) test, ellipsometry and atomic force microscopy (AFM). After that, the relationship of switchable behavior of PMOXA/PAA based coatings with PAA content and chain length was investigated through the change of thickness and WCA upon pH and ionic strength (I) trigger, which indicated that the change in thickness and WCA was triggered when PAA contents were increased as well as by increasing chain length of PAA in PMOXA/PAA based coatings. Finally, real-time adsorption/desorption of lysozyme (Lyso) on PMOXA/PAA based coatings was monitored using quartz crystal microbalance with dissipation monitoring (QCM-D). The results showed that the Lyso adsorption amount was increased upon increasing chain length and contents of PAA in PMOXA/PAA based coatings. The adsorbed Lyso was then efficiently desorbed by changing pH and I of medium with the maximum desorption (> 90% desorption percentage) observed for the suitable ratio of PMOXA and PAA while chain length of PAA was kept longer than that of PMOXA. Furthermore, the prepared coatings were found to repeatedly adsorb and desorb Lyso for four successive cycles of adsorption/desorption, which confirmed the stability of prepared coatings.

Room‐Temperature Self‐Healing and Recyclable Tough Polymer Composites Using Nitrogen‐Coordinated Boroxines

AbstractIn this paper, nitrogen‐coordinated boroxines are exploited for the fabrication of self‐healing and recyclable polymer composites with enhanced mechanical properties. The 3D polymer networks cross‐linked with nitrogen‐coordinated boroxines are first synthesized through the trimerization of ortho‐aminomethyl‐phenylboronic acid groups at the terminals of poly(propylene glycol) (PPG) chains, and subsequently, the mechanically robust polymer composites are fabricated by utilizing the complexation of nitrogen‐coordinated boroxine‐containing PPG (N‐boroxine‐PPG) with poly(acrylic acid) (PAA) and hydrogen‐bonding interactions between them. The N‐boroxine‐PPG is soft with a tensile strength of 0.19 MPa, whereas the tensile strengths of N‐boroxine‐PPG/PAA composites can be tailored to range from 1.7 to 12.7 MPa by increasing the PAA contents in the polymer composites. It is revealed that the amine ligands can facilitate the formation and dissociation of nitrogen‐coordinated boroxines at room temperature. Moreover, the reversibility of nitrogen‐coordinated boroxines and hydrogen‐bonding interactions enable multiple cycles of healing and recycling of the damaged N‐boroxine‐PPG/PAA composites. The healed and recycled N‐boroxine‐PPG/PAA polymer composites regain most of their mechanical strength.

Цифровое картографирование степени окультуренности пахотных почв Предсалаирской дренированной равнины

The article describes comparison of soil fertility indices (SFI) calculated for the ploughed layer of arable soils differing in soil organic matter (SOM) content: with high (5-8%) and medium (3-5%) SOM content. The studied soils were located on erosion-prone slope at different altitudes: soils with high SOM at 280-310 m, and soils with medium SOM at 190-280 m a.s.l. The study area was located in the interfluve area between the Irba and the Hiruzovka rivers in the Cis-Salair drained plain in the south-east of West Siberia. The soil types common there are Greyzemic Luvic Chernozems (Siltic, Aric, Pachic), Phaeozems (Siltic, Аric), Greyzemic Phaeozems Colluvic (Siltic, Taptomollic). The SFI were calculated in two steps. First, the relative indices (RI) for every agrochemical property, i.e. pHKCl, SOM, acetic acid extractable phosphorus (P) and exchangeable potassium (K), were calculated on the basis of respective minimal and optimal soil concentrations and crop requirements. Second, the SFI were calculated as sums of the relative indices divided by 4. The resultant SFI values were rated according to the scale where values below 0.4 indicate low fertility; values ranging 0.41-0.60 indicate moderate fertility, whereas values ranging 0.81-1.0 indicate high fertility. The digital maps of the RI and SFI were created using raster calculator in ENVI software, which allows performing mathematical operations with quantitative parameters of raster image pixels in GeoTIFF format. The values of relative indices in raster cells exceeding 1 (that is when factual content is higher than the optimal one) were substituted with 1 by specially developed program called ZChanger. Then the SFI map was created for erosion-risky slopes using as a basis the digital maps of the relative indices for pHKCl, SOM, P and K. Phosphorus was extracted by two different extragents, namely 0.5 М acetic acid (PAA) and 0.1 М ammonium malate (PAM). Soil fertility index was rated as medium irrespective of SOM content and soil type due to the high PAA content in soils with less SOM. It was found that when SFI were calculated using the data on easily available soil P, i.e. extracted with 0.015 М К2SO4 (PPS), then for most of the study area SFI can be rated as low, indicating the deficit of plant available phosphates in soils. High- and medium-SOM soils did not differ in рНKCL and PPS. The medium-SOM soils, such as agrochernozems, agro-grey and agro-dark-grey ones, had 1.7-2.2 lower SOM content as compared with the high-SOM soils such as agrochernozems. The reverse relation was found in labile P content: in soils with medium SOM level the PAA and PAM contents were 2 and 1.3 times higher than in high-SOM soils, respectively. In high-SOM agrochernozems PAA was lower than the optimal level (<20mg/100 g soil), while in medium-SOM soils it was higher. The PAM could be rated as medium. Exchangeable K in the arable soils was found to be unevenly distributed: in medium-SOM agrochernozems and agro-dark-grey soils exchangeable K was on average 1.2 times lower as compared with high-SOM agrochernozems, the difference with medium-SOM agro-grey soils being statistically not significant. Overall exchangeable K was lower than the optimal level (<30mg/100 g soil) Above-ground phytomass was found to be positively correlated with soil labile PPS (rs=0.41) and PAM (rs=0.33). The difference in aboveground phytomass produced by oats and peas mixture between high- and medium-SOM soils was not statistically significant.

Mechanical properties of bulk graphene oxide/poly(acrylic acid)/poly(ethylenimine) ternary polyelectrolyte complex.

Ternary complexes formed in a single pot process through the mixing of cationic (branched polyethylenimine, BPEI) and anionic (graphene oxide, GO, and poly(acrylic acid), PAA) aqueous solutions exhibit superior mechanical performance in comparison to their binary analogs. The composition of the ternary complex can be simply tuned through the composition of the anionic solution, which influences the water content and mechanical properties of the complex. Increasing the PAA content in the complex decreases the overall water content due to improved charge compensation with the BPEI, but this change also significantly improves the toughness of the complex. Ternary complexes containing ≤32 wt% PAA were too brittle to generate samples for tensile measurements, while extension in excess of 250% could be reached with 57 wt% PAA. From this work, the influence of GO and PAA on the mechanical properties of GO/PAA/BPEI complexes were elucidated with GO sheets acting to restrain the viscous flow and improve the mechanical strength at low loading (<12.6 wt%) and PAA more efficiently complexes with BPEI than GO to generate a less swollen and stronger network. This combination overcomes the brittle nature of GO-BPEI complexes and viscous creep of PAA-BPEI complexes. Ternary nanocomposite complexes appear to provide an effective route to toughen and strengthen bulk polyelectrolyte complexes.

Synthesis and Characterization of Alumina-Ceria Core-Shell Nanoparticles Using a Wet Chemical Method

In this study, α-Al2O3-CeO2 core-shell nanoparticles were synthesized from the cerium acetate and the commercial α-Al2O3 nanoparticles as the starting materials via a wet chemical method. Poly (acrylic acid) (PAA) as an additive compound was used for the surface modification of alumina nanoparticles. Also, the effects of PAA content, pH value and calcination temperature on the synthesis behavior of α-Al2O3-CeO2 nanoparticles were investigated. The formation of core-shell structure was investigated using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The results indicated that at the PAA=1.5 wt. %, pH=6 and calcination temperature=1150°C (as optimal conditions), the core-shell nanoparticles with alumina core and ceria shell and homogeneous size distribution were synthesized successfully.

Synthesis and Characterization of Multifunctional Interpenetrating Polymer and Its Applications in Protein Adsorption and Magnetite Loading

AbstractIn this study, we prepared interpenetrating polymers as nanocarrier systems for protein adsorption and superparamagnetic iron oxide nanoparticles (Fe3O4 NPs) loading. Interpenetrating polymer network (IPN) nanogels composed of crosslinked poly (N‐isopropylacrylamide) (PNIPAM) and poly (acrylic acid) (PAA) were firstly prepared, which possessed both pH and thermo‐responsive properties. On the one hand, the model protein (bull serum albumin (BSA)) was loaded into PNIPAM/PAA IPN nanogels. The effect of PAA content on the amount of BSA loading was investigated by controlling the temperatures and pH values. When the adsorption temperature was higher than the lower critical solution temperature (LCST) of PNIPAM and the pH value was lower than the pKa of PAA, it was more conductive to capture BSA. On the other hand, Fe3O4 NPs were encapsulated by in situ redox of iron cations in the interior of PNIPAM/PAA IPN nanogels. As the PAA content in the IPN nanogels increased and attracted more quantity of iron ions, the amount of loaded Fe3O4 NPs increased, which resulted in larger saturation magnetization of the magnetic nanogels but restricted the deswelling behaviors.

Design and development of pH-sensitive liposomes by evaluating the thermotropic behavior of their chimeric bilayers

This study is focused on mixed/chimeric advanced drug delivery nanosystems and specifically on pH-sensitive liposomes, combining lipids and pH-responsive amphiphilic block copolymers. Chimeric liposomes are composed of hydrogenated soy phosphatidylcholine (HSPC) and two different poly(n-butylacrylate)-b-poly(acrylic acid) (PnBA-b-PAA) block copolymers with 85 and 70% content of PAA, at six different molar ratios. PAA block exhibits pH responsiveness, because of the regulative group of –COOH. Chimeric bilayers are composed of HSPC and PnBA-b-PAA. Experiments are carried out by using differential scanning calorimetry (DSC) in order to investigate their thermotropic properties. DSC indicated disappearance of the pretransition effect in all chimeric lipid bilayers, at both buffers [phosphate buffer saline (PBS) and citrate buffer], and slight changes of the main transition temperature (T m). Contrariwise, the cooperativity (T 1/2) presented alterations between the two different buffers. Chimeric liposomes have been prepared and their physicochemical characteristics have been explored in PBS and citrate buffer by measuring the size, size distribution and ζ-potential. Liposomes are found to retain the mean value of their size during the stability studies. The physicochemical characteristics and the stability assessment of chimeric liposomes are correlated with DSC measurements of mixed bilayers. The incorporation of the appropriate amount of these novel pH-responsive block copolymers affects the cooperativity and the liposomal stabilization and imparts pH responsiveness (functionality), which was confirmed by performing experiments in acidic environment (citrate buffer). In conclusion, the results from DSC measurements provide useful information regarding the quality by design process for rationally preparing mixed/chimeric liposomal platforms to incorporate bioactive molecules.

Facile synthesis of hollow bioactive glass nanospheres with tunable size

Hollow nanospherical bioactive glasses were conducted though sol–gel process using poly(acrylic acid) (PAA) as the template. The incorporation of PAA was to form the core after air combustion, whereas the inorganic shell was produced by glass precursor. The mixture of different tetraorthosilicate (TEOS)/PAA contents into a glass network tailored the shell thickness, morphological, and structural properties of HBGs. The in vitro bioactivity evaluation confirmed that HBG2 sample exhibited good apatite formation ability, thereby denoting that the proposed method enhanced the potential application of HBGs in bone tissue regeneration and drug delivery.